Photoresist compositions and methods of use in high index immersion lithography

ABSTRACT

The present invention relates to a composition comprising a photoresist polymer and a fluoropolymer. In one embodiment, the fluoropolymer comprises a first monomer having a pendant group selected from alicyclic bis-hexafluoroisopropanol and aryl bis-hexafluoroisopropanol and preferably a second monomer selected from fluorinated styrene and fluorinated vinyl ether. The invention composition has improved receding contact angles with high refractive index hydrocarbon fluids used in immersion lithography and, thereby, provides improved performance in immersion lithography.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/163,649, filed on Jun. 27, 2008, which is a continuation of U.S.patent application Ser. No. 12/015,436, filed on Jan. 16, 2008, now U.S.Pat. No. 8,003,309, issued on Aug. 23, 2011, all of which areincorporated herein in their entireties.

TECHNICAL FIELD

The present invention relates to the fields of chemistry,photolithography, and semiconductor fabrication. More specifically, theinvention is directed to a resist composition comprising a resistpolymer and a fluoropolymer, which increases the contact angle of theresist film with hydrocarbon-based high refractive index immersionfluids. The invention further relates to the resist compositions thatcan be used in immersion lithography without the use of an additionaltopcoat and a method of forming a photolithographic image, where a highrefractive index immersion fluid, such as decahydronaphthalene ortetrahydrodicyclopentadiene, is interposed between the last lens fixtureof an exposure tool and the photoresist-coated wafer.

BACKGROUND OF THE INVENTION

The continuous drive to print smaller structures for advanced electronicdevice manufacturing requires the use of higher resolution opticallithography tools. Immersion lithography has extended 193 nm argonfluoride-based technology to 65 nm critical dimensions (half-pitch DRAM)and beyond by enabling lens designs with numerical apertures (NAs)greater than 1.0 and, thereby, increasing the resolution of opticalscanners. Immersion lithography also offers increased depth of focus,resulting in larger process windows. Immersion lithography involvesfilling the gap between the last lens element of the exposure tool andthe resist-coated substrate with an immersion fluid such as ultrapurewater. See, Hand, “Tricks with Water and Light: 193 nm Extension,”Semiconductor International, 27(2) (2004).

The practical numerical aperture limit of water-based immersion scannersis 1.35. In order to extend the capabilities of immersion lithography tolarger NA, higher refractive index lens and immersion fluids arerequired. Since NA is given by n_(medium) sin θ and sin θ reaches apractical limit as it approaches a value of 1, the refractive indices ofthe materials in the optical path effectively determine the numericalaperture. With water immersion, replacing air (n_(air)=1) with water(n_(water)=1.435) increased the maximum numerical apertures of imagingsystems from 0.93 (dry) to 1.35 (water immersion). Replacement of waterwith an immersion fluid with a higher refractive index will continuethis trend and enable even higher numerical aperture imaging systems.

Aqueous immersion fluids so far have shown limited refractive indices,high absorbance, and elevated viscosities (see, Costner et al., Proc.SPIE, 6153:61530B (2006)). Hydrocarbon-based immersion fluids such asdecahydronaphthalene, bicyclohexyl, andtricyclo[5.2.1^(1.7).0^(2,6)]decane (tetrahydrodicyclopentadiene) haveemerged as the most promising high index immersion fluids. Thesebicyclic and polycyclic saturated alkanes have shown refractive indicesup to 1.65 at 193 nm and transparencies that approach or even exceedwater (see, French et al., Proc. SPIE, 6154:615415 (2006); Wang et al.,Proc. SPIE., 6153:61530A (2006)).

One of the technical challenges facing liquid immersion lithography isthe diffusion between the photoresist components and the immersionmedium. That is, during the immersion lithographic process, thephotoresist components leach into the immersion medium and the immersionmedium permeates into the photoresist film. Such diffusion isdetrimental to photoresist imaging performance and might result indisastrous lens damage or contamination of the exposure tool. Inaddition, the surface energy of the photoresist must be engineered suchthat high contact angles with the immersion fluid are obtained. Meniscusforces are used to contain the immersion fluid beneath the immersionlens showerhead. At some wafer scan rate, the receding contact angle ofthe fluid falls to zero and a film of immersion fluid is left behind onthe wafer. This phenomenon is referred to as film pulling. It has beenshown that this residual fluid induces so-called watermark defects inthe final printed features (see, Wallraff et al., Proc. SPIE,6153:61531M (2006); Kocsis et al., Proc. SPIE, 6154:615409 (2006); andStepanenko et al., Proc. SPIE, 6153:615304 (2006)). The higher thereceding contact angle of the fluid on the surface, the faster the waferscan be scanned. (see, Schuetter et al., J. Microlith., Microfab.Microsys., 5:023002 (2006)).

One of the methods that has been quickly adopted by the resist communityto resolve these issues is the application of protective topcoatmaterials on top of the photoresist layer for the purpose of eliminatingdiffusion of materials from the photoresist layer underneath and tocontrol the surface energy and contact angle properties of the filmstack (see, Raub et al., J. Vac. Sci. Technol. B., 22:3459-3464 (2004);Kocsis et al., Proc. SPIE, 6154:615409 (2006); and Stepanenko et al.,Proc. SPIE, 6153:615304 (2006)). As described above, protective topcoatsare currently used in water immersion lithography. However, this addsadditional process steps and material cost to conventional lithography.Alternatively, topcoat-free photoresists have been developed in whichsurface-active fluoropolymer additives segregate to the photoresistsurface during film formation to control photoacid generator leachingand immersion fluid contact angles (see, Sanders et al., Proc. SPIE,6519, 651904 (2007) and Sanders et al., Microlithography World,16(3):8-13 (2007). These strategies have proven useful for waterimmersion lithography.

Water-based topcoat and additive materials are currently based onfluoropolymers with refractive indices around 1.45-1.55 at 193 nm. Asmentioned previously, the numerical aperture of the imaging system willbe limited by the lowest refractive index material in the imaging stack.The refractive index of the topcoat should be greater than the immersionfluid (in this case, greater than about 1.64). Current materials do notmeet these requirements.

In addition, the chemical and physical properties of the high refractiveindex hydrocarbon fluids are quite different from water. It has beenshown, for example, that the film pulling velocity of an immersion fluidwill be proportional to its surface tension to viscosity ratio (see,Schuetter et al., J. Microlith., Microfab., Microsys., 5:023002 (2006)).Since this ratio is roughly one-sixth that of water for the mostpromising high refractive index fluid candidates, film pulling has beenobserved at scan rates less than 100 mm/s (desired scan rates are 500mm/s). As a result, it expected that the prevention of film pulling withhigh refractive index fluids will not be able to be prevented withoutdramatically reducing scan rates and tool throughput. Partially wetapproaches are being explored in which small amounts of film pulling areallowed and the residual fluid is collected/removed after scanning Otherapproaches in which the entire wafer is submerged in a pool or puddle ofimmersion fluid are also being considered. In all of these applications,the photoresist surface must have very low interaction with thehydrocarbon immersion fluid. As a result, there exists a need forimproved materials with the appropriate optical properties which willallow for rapid scanning of wafers with controlled interaction with thehydrocarbon-based immersion fluids and reduced defectivity.

Bis-3,5-(hexafluoroisopropanol)cyclohexyl methacrylate andacrylate-based polymers have been developed for use as photoresists (seeHatakeyama et al. US 2005/0227173 and 2005/0227174) and topcoatmaterials for water-based immersion lithography (see Allen et al. US2006/0188804 A1, Allen et al. US 2007/0254235 A1, Maeda et al. WO2005/098541 A1, Hatakeyama et al. US 2006/0029884 A1, and Hata et al. US2006/0275697 A1). Additionally, α-trifluoromethyl(meth)acrylate polymersfeaturing bis-3,5-(hexafluoroisopropanol)cyclohexyl groups have beenexplored as photoresists (see, US 2006/0177765 A1 to Harada et al.) andtopcoats for water-based immersion lithography (see, US 2006/0292484 A1and US 2006/0292485 A1 to Ito et al. and WO 2005/098541 A1 to Maeda etal.). However, these materials have refractive indices too low to be ofuse in high index immersion lithography as topcoat materials.Bis-3,5-(hexafluoroisopropanol)cyclohexyl methacrylate polymers havebeen used as additives for topcoat-free resists in water immersionlithography with poor results (see, US 2007/0254235A1 to Allen et al.).These additives reduced photoacid generator (PAG) extraction into waterby only .about.15-20% (vide infra), which does not meet industryrequirements. In addition, typical hexafluoroisopropanol-functionalizedtopcoat materials have shown poor contact angles with hydrocarbon-basedhigh index fluids (vide infra).

As a result of these and other limitations, there is a need formaterials to impart good resistance to hydrocarbon-based immersionfluids and high contact angles with hydrocarbon-based immersion fluidsto photoresist materials in order to meet the requirements for highindex immersion lithography.

SUMMARY OF THE INVENTION

The present invention relates to a composition comprising a mixturecomprising a photoresist polymer and a fluoropolymer. In one embodiment,the fluoropolymer comprises a first monomer having a pendant groupselected from alicyclic bis-hexafluoroisopropanol and arylbis-hexafluoroisopropanol and a second monomer selected from fluorinatedstyrene and fluorinated vinyl ether. The invention composition hasimproved receding contact angles with high refractive index hydrocarbonfluids used in immersion lithography and, thereby, provides improvedperformance in immersion lithography. In another embodiment of thecomposition of the present invention, the photoresist polymer suitablycomprises repeat units having a carboxylic acid group that isnon-protected, partially protected or fully protected with a photoacidcleavable group. Suitable cleavable groups include esters, carbonates,acetals and ketal groups. In another embodiment, the fluoropolymercomprises a monomer selected from acrylate and methacrylate. In apreferred embodiment, the fluoropolymer comprises a monomer selectedfrom C₅₋₁₀ alicyclic bis-hexafluoroisopropanol methacrylate and C₅₋₁₀alicyclic bis-hexafluoroisopropanol acrylate. In another embodiment, thefluoropolymer comprises a monomer having the pendant group C₆₋₁₀ arylbis-hexafluoroisopropanol.

The present invention also relates to the process for forming aphotoresist image on a substrate using the composition of the presentinvention. The composition of the present invention provides highreceding contact angles when used in immersion lithography thusproviding improved performance.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail with reference tothe drawings, wherein:

FIG. 1A shows the static contact angle (θ_(e)) to be the angle when allparticipating phases (i.e., air, water and resist film) have reachedtheir natural equilibrium positions and the three phase line is notmoving.

FIG. 1B shows how static advancing (θ_(s)t) and receding (θ_(r)T)contact angles are measured with the tilting stage setup.

FIG. 2 shows a comparison between the contact angles of thebis-fluoroalcohol-based polymer relative to otherfluoroalcohol-containing polymers using water and organic high indexfluids (JSR HIL-001 and bicyclohexyl).

FIG. 3 shows the contact angles of invention fluoroalcohol polymersusing water and organic high index fluids (JSR HIL-001 andbicyclohexyl).

FIG. 4 shows 193 nm contrast curves of resist compositions with andwithout a fluoroalcohol polymer of the present invention.

FIG. 5 shows VASE analysis of the film structure of a composition of thepresent invention. Several different model profiles are fitted to theexperimental data with the most accurate profile exhibiting the lowestfitting mean square error.

FIG. 6 shows the extraction of PAG from the composition of the presentinvention into fluids.

FIG. 7 shows comparative immersion interference lithographic imagingresults of the composition of the present invention using JSR HIL-001high index immersion fluid and water.

FIG. 8 shows the optical properties of fluoropolymers of the presentinvention.

FIG. 9 shows contrast curves of compositions of the present invention.

FIG. 10 shows immersion interference lithographic imaging results of twocompositions of the present invention using high index immersion fluid.

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise indicated, this invention is not limited to specificcompositions, components, or process steps. It should also be noted thatthe singular forms “a” and “the” are intended to encompass pluralreferents, unless the context clearly dictates otherwise. Theterminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting.

In this specification and in the claims that follow, reference will bemade to a number of terms, which shall be defined to have the followingmeanings:

As used herein, the phrase “having the formula” or “having thestructure” is not intended to be limiting and is used in the same waythat the term “comprising” is commonly used.

The term “alkyl” as used herein refers to a linear or branched,saturated hydrocarbon substituent that generally, although notnecessarily, contains 1 to about 24 carbon atoms, such as methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, octyl, decyl,tetradecyl, hexadecyl, eicosyl, tetracosyl, and the like. Generally,although again not necessarily, alkyl groups herein contain 1 to about12 carbon atoms, preferably, 1-6 carbons. The term “cycloalkyl” intendsa cyclic alkyl group, typically having 3 to 12, preferably 3 to 8,carbon atoms. The term “substituted alkyl” refers to alkyl substitutedwith one or more substituent groups, i.e., wherein a hydrogen atom isreplaced with a non-hydrogen substituent group, and the terms“heteroatom-containing alkyl” and “heteroalkyl” refer to alkylsubstituents in which at least one carbon atom is replaced with aheteroatom such as O, N, or S. If not otherwise indicated, the terms“alkyl” includes linear, branched and cyclic alkyl and lower alkyl,respectively.

The term “alkylene” as used herein refers to a difunctional linear orbranched saturated hydrocarbon linkage, typically although notnecessarily containing 1 to about 24 carbon atoms, such as methylene,ethylene, n-propylene, n-butylene, n-hexylene, decylene, tetradecylene,hexadecylene, and the like. Preferred alkylene linkages contain 1 toabout 12 carbon atoms, preferably 1 to 6 carbon atoms. The term“substituted alkylene” refers to an alkylene linkage substituted withone or more substituent groups, i.e., wherein a hydrogen atom isreplaced with a non-hydrogen substituent group, and the terms“heteroatom-containing alkylene” and “heteroalkylene” refer to alkylenelinkages in which at least one carbon atom is replaced with aheteroatom. If not otherwise indicated, the terms “alkylene” includeslinear, branched and cyclic alkylene and lower alkylene, respectively.

The term “alkoxy” as used herein refers to a group —O-alkyl wherein“alkyl” is as defined above.

The term “alicyclic” is used to refer to cyclic, non-aromatic compounds,substituents and linkages, e.g., cycloalkanes and cycloalkenes,cycloalkyl and cycloalkenyl substituents linkages. Often, the termrefers to polycyclic compounds, substituents, and linkages, includingbridged bicyclic, compounds, substituents, and linkages. Preferredalicyclic moieties herein contain 3 to about 30, typically 5 to about14, carbon atoms. It will be appreciated that the term “cyclic,” as usedherein, thus includes “alicyclic” moieties.

The term “heteroatom-containing” as in a “heteroatom-containing alkylgroup” (also termed a “heteroalkyl” group) refers to a molecule, linkageor substituent in which one or more carbon atoms are replaced with anatom other than carbon, e.g., nitrogen, oxygen, sulfur, phosphorus orsilicon, typically nitrogen, oxygen or sulfur. Similarly, the term“heteroalkyl” refers to an alkyl substituent that isheteroatom-containing; the term “heterocyclic” refers to a cyclicsubstituent that is heteroatom-containing Examples of heteroalkyl groupsinclude alkoxyalkyl, alkylsulfanyl-substituted alkyl, and the like.

Unless otherwise indicated, the term “hydrocarbyl” is to be interpretedas including substituted and/or heteroatom-containing hydrocarbylmoieties. “Hydrocarbyl” refers to univalent hydrocarbyl radicalscontaining 1 to about 30 carbon atoms, preferably 1 to about 18 carbonatoms, most preferably 1 to about 12 carbon atoms, including linear,branched, cyclic, alicyclic, and aromatic species.

By “substituted” as in “substituted alkyl,” and the like, as alluded toin some of the aforementioned definitions, is meant that in the alkyl,or other moiety, at least one hydrogen atom bound to a carbon (or other)atom is replaced with a non-hydrogen substituent. Examples of suitablesubstituents herein include halo, hydrido (H—), sulfhydryl, C₁-C₁₂alkoxy, acyl (including C₂-C₁₂ alkylcarbonyl (—CO-alkyl)), acyloxy(—O-acyl), C₂-C₁₂ alkoxycarbonyl (—(CO)—O-alkyl), hydroxycarbonyl(—COOH), carbamoyl (—(CO)—NH₂), substituted C₁-C₁₂ alkylcarbamoylincludes (—(CO)—NH(C₁-C₁₂ alkyl)) and (—(CO)—N(C₁-C₁₂ alkyl)₂), formyl(—(CO)—H), amino (—NH₂), mono- and di-(C₁-C₁₂ alkyl)-substituted amino,mono- and C₂-C₁₂ alkylamido (—NH—(CO)-alkyl), imino (—CR.dbd.NH whereR=hydrogen, C₁-C₁₂ alkyl, etc.), alkylimino (—CR.dbd.N(alkyl), whereR=hydrogen, alkyl, etc.), C₁-C₂₀ alkylsulfanyl (—S-alkyl; also termed“alkylthio”), C₅-C₁₈ arylsulfanyl (—S-aryl; also termed “arylthio”),C₁-C₂₀ alkylsulfinyl (—(SO)-alkyl), C₁-C₂₀ alkylsulfonyl(SO.sub.2-alkyl), hydroxysulfonyl (—SO₂—OH), phosphono (—P(O)(OH)₂), andthe hydrocarbyl moieties C₁-C₂₄ alkyl (preferably C.sub.1-C.sub.12alkyl). In addition, the aforementioned functional groups may, if aparticular group permits, be further substituted with one or moreadditional functional groups or with one or more hydrocarbyl moietiessuch as those specifically enumerated above. Examples of linking groupsinclude oxy (—O—), thio (—S—), carbonyloxy (—COO—), oxycarbonyl (—OCO—),sulfonyl (—SO₂—), carbonylthio (—COS—), carbonylamino (—CONR—) where Ris hydrido or alkyl, alkylene, and phenylene (—C₆H₄—).

The term “fluorinated” refers to replacement of one or more hydrogenatoms in a molecule or molecular segment with one or more fluorineatoms, and includes perfluorinated moieties. The term “perfluorinated”is also used in its conventional sense to refer to a molecule ormolecular segment wherein all hydrogen atoms are replaced with fluorineatoms. Thus, a “fluorinated” methyl group encompasses —CH₂F and —CHF₂ aswell as the “perfluorinated” methyl group, i.e., —CF₃ (trifluoromethyl).The term “fluoroalkyl” refers to a fluorinated alkyl group, the term“fluoroalkylene” refers to a fluorinated alkylene linkage, the term“fluoroalicyclic” refers to a fluorinated alicyclic moiety, and thelike.

A fluoroalcohol is defined as an organic compound bearing a hydroxylgroup wherein one or more non-hydroxyl group hydrogen atoms are replacedwith fluorine atoms. The fluoroalcohol may be comprised of a linear,branched, cyclic, polycyclic, or aromatic structure. Many non-limitingexamples of such fluoroalcohols may be found in Ito, “ChemicalAmplification Resists for Microlithography,” Adv. Polym. Sci.,172:37-245 (2005).

“Optional” or “optionally” means that the subsequently describedcircumstance may or may not occur, so that the description includesinstances where the circumstance occurs and instances where it does not.For example, the phrase “optionally substituted” means that anon-hydrogen substituent may or may not be present on a given atom, and,thus, the description includes structures wherein a non-hydrogensubstituent is present and structures wherein a non-hydrogen substituentis not present.

The term “acid-labile” refers to a molecular segment containing at leastone covalent bond that is cleaved upon exposure to acid. Typically, thereaction of acid-cleavable groups herein with photogenerated acid occursonly, or is promoted greatly by, the application of heat. Those skilledin the art will recognize the various factors that influence the rateand ultimate degree of cleavage of acid-cleavable groups as well as theissues surrounding integration of the cleavage step into a viablemanufacturing process. The product of the cleavage reaction is generallyan acidic group, which, when present in sufficient quantities, impartssolubility to the polymers of the invention in basic aqueous solutions.

Analogously, the term “acid-inert” refers to a substituent that is notcleaved or otherwise chemically modified upon contact withphotogenerated acid.

The terms “photogenerated acid” and “photoacid” are used interchangeablyherein to refer to the acid that is created upon exposure of the presentphotoresist compositions to radiation, by virtue of the photoacidgenerator contained in the compositions.

The term “substantially transparent” as used to describe a polymer thatis “substantially transparent” to radiation of a particular wavelengthrefers to a polymer that has an absorbance of less than about7.0/micron, preferably less than about 3.0/micron, most preferably lessthan about 1.5/micron, at a selected wavelength.

For additional information concerning terms used in the field oflithography and lithographic compositions, see Introduction toMicrolithography, Eds. Thompson et al. (Washington, D.C.: AmericanChemical Society, 1994).

The present invention relates to a composition comprising a mixturecomprising a photoresist polymer and a fluoropolymer. In one embodiment,the fluoropolymer is a polymer comprising a first monomer having apendant group selected from alicyclic bis-hexafluoroisopropanol and arylbis-hexafluoroisopropanol and preferably a second monomer selected fromfluorostyrene and fluorinated vinyl ether. The two hexafluoroisopropanolsubstituents are attached to the alicyclic ring or aryl ring which is inturn attached to the polymer. The inventive composition comprising thesecomponents has improved receding contact angles with high refractiveindex hydrocarbon fluids used in immersion lithography and therebyprovides improved performance in immersion lithography. In a preferredembodiment, the fluoropolymer comprises a monomer selected from C₅₋₁₀alicyclic bis-hexafluoroisopropanol methacrylate and C₅₋₁₀ alicyclicbis-hexafluoroisopropanol acrylate.

In another embodiment of the present invention, the fluoropolymercomprises a monomer having a formula selected from:

wherein R₁, R₂, R₄, and R₅ are independently selected from hydrido andfluorine; R.sub.3 and R.sub.6 are independently selected from hydrido,fluorine, C1-C4 alkyl optionally fluorinated e.g., methyl andtrifluoromethyl;

X₁ is a linking group independently selected from oxy, thio,carbonyloxy, oxycarbonyl, carbonylthio, sulfonyl, carbonylamino,alkylene, cycloalkylene optionally substituted with fluorine,alkyleneoxyalkylene, hetereoalkylene, phenylene, fluorinated phenylene,naphthylene or fluorinated naphthylene; and

Y₁ and Y₂ are independently selected from C₁₋₁₀ alkylene andcycloalkylene and phenylene and naphthylene each optionally substitutedwith fluorine. Preferably, the polymer comprises a second monomerselected from a monomer having the formula:

wherein

R₇, R₈, R₁₀, and R₁₁ are independently selected from hydrido and fluoro;

R₉ and R₁₂ are independently selected from hydrido, fluoro, C1-C4 alkyloptionally fluorinated e.g., methyl, and trifluoromethyl;

X₃ and X₄ are linking groups independently selected from oxy, thio,carbonyloxy, carbonyloxyalkylene, carbonylthio, sulfonyl, carbonylamino,alkylene and cycloalkylene each optionally substituted with fluorine,alkyleneoxyalkylene, hetereoalkylene, phenylene, fluorinated phenylene,naphthylene and fluorinated naphthylene; m and n are each independentlyselected from 0 and 1;

Y₃ is a substitutent which includes at least one of the followinggroups: (i) an acid-labile group selected from alkoxycarbonyl, alkoxy,cycloalkoxy, alkyl, fluorinated alkyl, fluorinated alkoxy andfluorinated alkoxycarbonyl and/or (ii) an acidic functionalitycontaining group selected from hydroxycarbonyl, hydroxysulfonyl,fluorinated hydroxyalkyl, hydroxyphenyl, hydroxynaphthyl, fluorinatedsulfonamidyl, hydroxyamidyl, carbamoyl and alkylcarbamoyl; and

Y₄ is selected from hydrido, fluoro, fluoroalcohol (hydroxyfluoroalkyl,e.g., bis-hexafluoroisopropanol), alkyl, fluorinated alkyl, fluorinatedheteroalkyl, fluorinated phenyl and fluorinated naphthyl.

In one preferred embodiment, X₁ is selected from oxy, carbonyloxy,carbonylthio, fluorinated C₅₋₈ cycloalkylene and fluorinated phenylene.In another preferred embodiment, Y₁ and Y₂ are selected from C₅₋₈cycloalkylene and phenylene each optionally substituted with fluorine.

In one embodiment M1A and M1B together comprise 20-100 mole % of therepeat units in the fluoropolymer, and in another embodiment, the sum ofthe mole % of the repeat units of M1A, M1B, M2, and M3 comprises atleast about 80 mole % of the repeat units in the fluoropolymer.

The present invention further relates to a process for forming aphotoresist image in a film positioned on the surface of a substratecomprising: a) forming a film of the invention composition on thesurface of a substrate; b) patternwise exposing the film coated on thesubstrate to imaging irradiation; c) optionally baking the exposedsubstrate; d) contacting the coated substrate with a developer, suitablyan aqueous alkaline developer, wherein a portion of the photoresistlayer is removed from the substrate, thereby forming a patternedphotoresist layer on the substrate.

Preferably, in the process of the invention, the film on the substrateis covered with a thin layer of fluid (e.g., water or a hydrocarbonfluid) prior to exposure to imaging radiation. Preferably, the fluid isa hydrocarbon fluid. It is to be understood that the hydrocarbon fluidneed not be a single component fluid. It may comprise 1 or morehydrocarbon compounds (as long as at least 1 is a liquid at roomtemperature), surfactants, flow modifiers, stabilizers, and refractiveindex modifiers such as nanoparticles, ionic liquids, or coordinationcompounds.

In the process of the present invention, the fluoropolymer is mixed withthe photoresist polymer. The mixture is then coated onto the surface ofa substrate. When the mixture is coated as a resist film on a substrate,the fluoropolymer segregates to the surface of the film to form anenrichment layer over the entire film, which acts as an in-situ topcoat.The enrichment layer suitably will have a thickness of from about 1 toabout 5 nm. The design scheme leads to high contact angles whilemaintaining good lithographic performance. In an alternative embodiment,the fluoropolymer comprising a pendant group of arylhexafluoroisopropanol with or without a second monomer as defined above,can be used as a topcoat over a photoresist layer in immersionlithography suitably with UV radiation having a wavelength less than 200nm.

It has been found that high receding contact angles are required toavoid film pulling behind the meniscus as the wafer travels underneaththe immersion showerhead. Film pulling results in a trail of fluid filmor droplets being left behind on the wafer. Subsequent evaporation ofthis residual fluid has been positively correlated with an increasednumber of defects (so-called watermarks) in the printed patterns. Inaddition, the heat of evaporation of the immersion fluid results inwafer cooling and may cause thermal shrinkage (which leads to overlayproblems). The scan rate at which film pulling begins varies accordingto the immersion fluid, showerhead, and fluid management strategyemployed by the immersion tool. Given the lower surface tension andhigher viscosities of the hydrocarbon immersion fluids relative towater, film pulling is an issue at scan rates suitable formanufacturing. In this case, one of the roles of the fluoropolymerenrichment layer is to reduce the number of defects caused by this filmof hydrocarbon fluid by providing a non-interacting surface.

In the process of the invention, a film of the invention composition isformed on a substrate, suitably a silicon substrate, by art knownmethods such as spin coating. The substrate can be uncoated oroptionally coated with a layer of material such as anti-reflectivecoating, hardmask, transfer/planarization layer, low temperature oxideor the like. Optionally, after the film has been formed on thesubstrate, it can be baked at an elevated temperature of usually between90 and 140° C. Suitably, the film on the substrate is then covered witha thin layer of immersion fluid suitably, a hydrocarbon fluid by artknown methods. The film is then exposed patternwise to radiation,suitably shorter wavelength ultraviolet radiation (e.g., <200 nm such as193 nm) or with extreme ultraviolet radiation or electron beam. Afterexposure to radiation, the hydrocarbon fluid may be removed and the filmis then optionally baked at an elevated temperature. The substrate isthen developed suitably by exposure to development fluid to form patternin the film. The pattern can then be transferred to the underlyingsubstrate by art known methods such as reactive ion etching.

The present invention is also directed to fluoropolymers including apolymeric or oligomeric compound having one of the followingcompositions:

Polymer 1: x=100 mole %;

wherein x:y=99-90 mole %: 1-10 mole % and x+y>75 up to 100 mole %; asexemplified by:

Polymer 2: x=95 mole %, y=5 mole %;

wherein x:y=99-40 mole %: 1-60 mole % and x+y does not exceed 100 mole%; as exemplified by:

Polymer 3: x=80 mole %, y=20 mole %;

wherein x:y=99-40 mole %: 1-60 mole % and x+y does not exceed 100 mole%; as exemplified by:

Polymer 4: x=70 mole %, y=30 mole %;

wherein x:y=99-40 mole %: 1-60 mole % and x+y does not exceed 100 mole%; as exemplified by:

Polymer 5: x=70 mole %, y=30 mole %;

Polymer 6: x=100 mole %;

wherein x:y=99-40 mole %: 1-60 mole % and x+y does not exceed 100 mole%; as exemplified by:

Polymer 7: x=50 mole %, y=50 mole %;

wherein x:y=99-40 mole %: 1-60 mole % and x+y does not exceed 100 mole%; as exemplified by:

Polymer 8: x=50 mole %, y=50 mole %;

Polymer 9: x=100 mole %;

wherein x:y=75-55 mole %: 25-45 mole % and x+y does not exceed 100 mole%; as exemplified by:

Polymer 10: x=66 mole %, y=33 mole %;

wherein x:y=75-55 mole %: 25-45 mole % and x+y does not exceed 100 mole%; as exemplified by:

Polymer 11: x=66 mole %, y=33 mole %;

wherein x:y:z=74-25 mole %: 1-45 mole %: 25-45 mole %; and x+y+z doesnot exceed 100 mole %; as exemplified by:

Polymer 12: x=29 mole %, y=29 mole %; z=42 mole %;

wherein x:y:z=75-20 mole %: 1-55 mole %: 25-45 mole % and x+y+z does notexceed 100 mole %; as exemplified by:

Polymer 13: x=36 mole %, y=27 mole %; z=37 mole %.

The fluoropolymer additive of this invention may be mixed with anydesired photoresist polymer in the formulation of the invention resistcomposition. Photoresist polymers are polymers which experience a changein solubility in a development fluid after exposure to radiation such asUV, x-ray or electron beam radiation. Suitably, in the exposed portionof the photoresist polymer, the radiation causes a portion of a pendantgroup, such as a photoacid cleavable pendant ester group, to cleave toachieve increased solubility of the exposed portion of the polymer inthe development fluid. Alternatively, the radiation can cause theexposed portion of the photoresist polymer to become less soluble in adevelopment fluid. Preferably, the photoresist polymer is a chemicalamplification photoresist that is imagable with shorter wavelengthultraviolet radiation (e.g., <200 nm wavelength) or with extremeultraviolet radiation (EUV) or electron beam radiation. Examples ofsuitable chemically amplified resists are described in Ito, “ChemicalAmplification Resists for Microlithography,” Advances in PolymerScience, 172:37-245 (2005). The fluoropolymer of this invention mayconstitute about 0.01 percent by weight to about 20 percent by weight ofthe solid contents of the invention composition. Preferably, thefluoropolymer is less than about 5 percent by weight of the solidcontents of the invention composition.

In the present invention, the photoresist polymer which includesoligomers can represent up to about 99 percent by weight of the solidsincluded in the composition, and the photoacid generator can representapproximately 0.1 percent by weight to 25 percent by weight of thesolids contained in the composition.

Suitable photoresist polymers include acrylates, methacrylates,cycloolefin polymers, cycloolefin maleic anhydride copolymers,cycloolefin vinyl ether copolymers, siloxanes, silsesquioxanes,carbosilanes. Other photoresist polymers which are oligomers includepolyhedral oligomeric silsesquioxanes, carbohydrates, and other cagecompounds. These polymers or oligomers are appropriately functionalizedwith aqueous base soluble groups, acid-labile groups, polarfunctionalities, silicon containing groups as needed.

The photoacid generator may be any compound that, upon exposure toradiation, generates a strong acid and is compatible with the othercomponents of the photoresist composition. Examples of preferredphotochemical acid generators (PAGs) include, but are not limited to,sulfonates, onium salts, aromatic diazonium salts, sulfonium salts,diaryliodonium salts and sulfonic acid esters of N-hydroxyamides orN-hydroxyimides, as disclosed in U.S. Pat. No. 4,731,605. Any PAG(s)incorporated into the present photoresists should have high thermalstability, i.e., be stable to at least 140° C., so they are not degradedduring pre-exposure processing.

Any suitable photoacid generator can be used in the photoresistcompositions of the invention. Typical photoacid generators include,without limitation: (1) sulfonium salts, such as triphenylsulfoniumperfluoromethanesulfonate (triphenylsulfonium triflate),triphenylsulfonium perfluorobutanesulfonate, triphenylsulfoniumperfluoropentanesulfonate, triphenylsulfonium perfluorooctanesulfonate,triphenylsulfonium hexafluoroantimonate, triphenylsulfoniumhexafluoroarsenate, triphenylsulfonium hexafluorophosphate,triphenylsulfonium bromide, triphenylsulfonium chloride,triphenylsulfonium iodide, 2,4,6-trimethylphenyldiphenylsulfoniumperfluorobutanesulfonate, 2,4,6-trimethylphenyldiphenylsulfoniumbenzenesulfonate, tris(t-butylphenyl)sulfonium perfluorooctanesulfonate,diphenylethylsulfonium chloride, and phenacyldimethylsulfonium chloride;(2) halonium salts, particularly iodonium salts, includingdiphenyliodonium perfluoromethanesulfonate (diphenyliodonium triflate),diphenyliodonium perfluorobutanesulfonate, diphenyliodoniumperfluoropentanesulfonate, diphenyliodonium perfluorooctanesulfonate,diphenyliodonium hexafluoroantimonate, diphenyliodoniumhexafluoroarsenate, bis-(t-butylphenyl)iodonium triflate, andbis-(t-butylphenyl)-iodonium camphanylsulfonate; (3)α,α′-bis-sulfonyl-diazomethanes, such asbis(p-toluenesulfonyl)diazomethane, methylsulfonylp-toluenesulfonyldiazomethane,1-cyclohexylsulfonyl-1-(1,1-dimethylethylsulfonyl)diazomethane, andbis(cyclohexylsulfonyl)diazomethane; (4) trifluoromethanesulfonateesters of imides and hydroxyimides, e.g.,α-(trifluoromethylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide(MDT); (5) nitrobenzyl sulfonate esters, such as 2-nitrobenzylp-toluenesulfonate, 2,6-dinitrobenzyl p-toluenesulfonate, and2,4-dinitrobenzyl p-trifluoromethylbenzene sulfonate; (6)sulfonyloxynaphthalimides such as N-camphorsulfonyloxynaphthalimide andN-pentafluorophenylsulfonyloxynaphthalimide; (7) pyrogallol derivatives(e.g., trimesylate of pyrogallol); (8) naphthoquinone-4-diazides; (9)alkyl disulfones; (10) s-triazine derivatives, as described in U.S. Pat.No. 4,189,323; and miscellaneous sulfonic acid generators includingt-butylphenyl-α-(p-toluenesulfonyloxy)-acetate,t-butyl-α-(p-toluenesulfonyloxy)acetate, and N-hydroxy-naphthalimidedodecane sulfonate (DDSN), and benzoin tosylate.

Other suitable photoacid generators are disclosed in Reichmanis et al.,Chemistry of Materials, 3:395 (1991) and in U.S. Pat. No. 5,679,495 toYamachika et al. Additional suitable acid generators useful inconjunction with the compositions and methods provided herein will beknown to those skilled in the art and/or are described in the pertinentliterature.

The remainder of the invention composition is suitably composed of asolvent and may additionally, if necessary or desirable, includecustomary additives such as, but not limited to, dissolutionsinhibitors, dyes, sensitizers, additives used as stabilizers,dissolution modifying additives, and acid-diffusion controlling agents,bases/quenchers, coating aids such as surfactants or anti-foamingagents, crosslinking agents, photospeed control agents, adhesionpromoters and plasticizers.

In addition to the above components, the photoresist compositionsprovided herein generally include a casting solvent to dissolve theother components so that the overall composition may be applied evenlyon the substrate surface to provide a defect-free coating.

The choice of solvent is governed by many factors not limited to thesolubility and miscibility of resist components, the coating process,and safety and environmental regulations. Additionally, inertness toother resist components is desirable. It is also desirable that thesolvent possess the appropriate volatility to allow uniform coating offilms yet also allow significant reduction or complete removal ofresidual solvent during the post-application bake process. See, e.g.,Introduction to Microlithography, Eds. Thompson et al., citedpreviously. Where the photoresist composition is used in a multilayerimaging process, the solvent used in the imaging layer photoresist ispreferably not a solvent to the underlayer materials, otherwise theunwanted intermixing may occur. The invention is not limited toselection of any particular solvent. Suitable casting solvents maygenerally be chosen from ether-, ester-, hydroxyl-, andketone-containing compounds, or mixtures of these compounds. Examples ofappropriate solvents include carbon dioxide, cyclopentanone,cyclohexanone, ethyl 3-ethoxypropionate (EEP), a combination of EEP andγ-butyrolactone (GBL), lactate esters such as ethyl lactate, alkyleneglycol alkyl ether esters such as PGMEA, alkylene glycol monoalkylesters such as methyl cellosolve, butyl acetate, and 2-ethoxyethanol.Preferred solvents include ethyl lactate, propylene glycol methyl etheracetate, ethyl 3-ethoxypropionate and their mixtures. The above list ofsolvents is for illustrative purposes only and should not be viewed asbeing comprehensive nor should the choice of solvent be viewed aslimiting the invention in any way. Those skilled in the art willrecognize that any number of solvents or solvent mixtures may be used.

Greater than 50 percent of the total mass of the resist composition istypically composed of the solvent, preferably greater than 80 percent.

Other customary additives include dyes that may be used to adjust theoptical density of the formulated resist and sensitizers which enhancethe activity of photoacid generators by absorbing radiation andtransferring it to the photoacid generator. Examples include aromaticssuch as functionalized benzenes, pyridines, pyrimidines, biphenylenes,indenes, naphthalenes, anthracenes, coumarins, anthraquinones, otheraromatic ketones, and derivatives and analogs of any of the foregoing.

In addition to the above, a wide variety of art known compounds withvarying basicity may be used as stabilizers in the inventioncomposition. Art known surfactants may be used to improve coatinguniformity, and a wide variety of anti-foaming agents may be employed tosuppress coating defects. Adhesion promoters may be used as well; again,a wide variety of compounds may be employed to serve this function. Awide variety of monomeric, oligomeric, and polymeric plasticizers suchas oligo- and polyethyleneglycol ethers, cycloaliphatic esters, andnon-acid reactive steroidally derived materials may be used asplasticizers, if desired. However, neither the classes of compounds northe specific compounds mentioned above are intended to be comprehensiveand/or limiting. One skilled in the art will recognize the wide spectrumof commercially available products that may be used to carry out thetypes of functions that these customary additives perform.

Typically, the sum of all customary additives will comprise less than 20percent of the solids included in the resist formulation, preferably,less than about 5 percent.

The present invention, as mentioned above, is directed to an inventivecomposition which has a low surface energy, i.e., high contact angle.The structures presented above have been characterized for static,advancing, and receding contact angles.

EXAMPLES

The following examples are intended to provide those of ordinary skillin the art with a complete disclosure and description of how to prepareand use the compositions disclosed and claimed herein. Efforts have beenmade to ensure accuracy with respect to measured numbers, but allowanceshould be made for the possibility of errors and deviations. Unlessindicated otherwise, parts are parts by weight, temperature is in ° C.and pressure is at or near atmospheric.3,5-bis(1,1,1,3,3,3-hexafluoropropan-2-ol-2-yl)cyclohex-1-ylmethacrylate,3,5-bis(1,1,1,3,3,3-hexafluoropropan-2-ol-2-yl)cyclohex-1-yltrifluoromethacrylate,3,5-bis(1,1,1,3,3,3-hexafluoropropan-2-ol-2-yl)phenyl methacrylate,t-butyl trifluoromethacrylate, 1,1,1,3,3,3-hexafluoroisoprop-2-ylmethacrylate, 1,1,1,3,3,3-hexafluoroisoprop-2-yl trifluoromethacrylate,and 1,1,1,2,2,3,3,4,4-nonafluorohex-6-yl vinyl ether, were obtained fromCentral Glass (Japan). Additionally, all the other starting materialswere obtained commercially or were synthesized using known procedures.

Where appropriate, the following techniques and equipment were utilizedin the examples: ¹H and ¹³C NMR spectra were obtained at roomtemperature on an Avance 400 spectrometer. Quantitative ¹³C NMR was runat room temperature in acetone-d6 in an inverse-gated .sup.1H-decoupledmode using Cr(acac)₃ as a relaxation agent on an Avance 400spectrometer. For polymer composition analysis ¹⁹F NMR (379 MHz) spectrawere also obtained using a Bruker Avance 400 spectrometer.Thermo-gravimetric analysis (TGA) was performed at a heating rate of 5°C./min in N₂ on a TA Instrument Hi-Res TGA 2950 ThermogravimetricAnalyzer. Differential scanning calorimetry (DSC) was performed at aheating rate of 10° C./min on a TA Instruments DSC 2920 modulateddifferential scanning calorimeter. Molecular weights were measured intetrahydrofuran (THF) on a Waters Model 150 chromatograph relative topolystyrene standards. IR spectra were recorded on a Nicolet 510 FT-IRspectrometer on a film cast on a KBr plate. Optical density orabsorbance measurements at 193 nm were performed using a Varian CaryModel 400 spectrometer on multiple thicknesses on quarts wafers. Filmthickness was measured on a Tencor alpha-step 2000 or Nanospec. A quartzcrystal microbalance (QCM) with a MAXTEC Inc. PLO-10 Phase lockoscillator was used to study the dissolution kinetics of the resistfilms in an aqueous 0.26N tetramethylammonium hydroxide (TMAH) solution(CD-26). Lithographic evaluation was performed on a 0.6NA 193 nm ISIministepper dry exposure tool or a 193 nm interferometric immersionexposure tool.

Contact angles were measured on an OCA video based contact angle systemfrom FDS Future Digital Scientific Corporation, using the sessile dropmethod. The advancing and receding contact angles were measured using atilting stage. Referring to FIG. 1, in the present invention we presentthe static contact angle (θ_(static) or θ_(e)), advancing contact angle(θ_(adv) or θ_(s)T), receding contact angle (θ_(rec) or θ_(r)T), andtilt angle (θ_(tilt)). FIG. 1A shows the static contact angle to be theangle when all participating phases (i.e., air, water and resist film)have reached their natural equilibrium positions and the three phaseline is not moving. Reported are static contact angles with a calculatedaverage from 5-10 measurements of a 5 μL ionized water drop. FIG. 1Bshows how advancing (θ_(adv)) and receding (θ_(rec)) static contactangles are measured with the tilting stage setup. A 50 μL drop is placedon the substrate, the substrate is thereafter tilted until the dropletstarts moving. The tilt angle (θ_(tilt)), θ_(adv) and θ_(rec) aremeasured just before the drop starts moving. The presented numbers arecalculated from and average of 3-5 separate measurements.

One of the main objectives of using a topcoat is to prevent leaching ofextractables from the resist into the immersion liquid. Extraction ofresist components into water was performed using WEXA (Water ExtractionApparatus, see, Allen et. al., J. Photopolym. Sci. & Technol., 18(5):615-619 (2005)). Selected materials in the present invention wereset in contact with immersion fluid in a controlled reproducible manner(time, speed, volume, contact area etc.). In the case of water, thefluid was thereafter collected and directly analyzed for extractables byMPI Research (State College, Pa.) using LC/MS/MS. For hydrocarbonfluids, the collected fluid was evaporated by blowing a stream ofultrapure argon over the fluid at a temperature between 20 and 60° C.until dryness. Then the sample was redissolved in 5 grams of deionizedultrapure water. The resulting aqueous sample was then directly analyzedfor extractables by MPI Research using LC/MS/MS. Reported are the amountsulfonate extractables originating from the PAG (photo acid generator)that is a component of the resist. For ease of understanding, the amountis reported as percent extractable reduction using an additive coveredby the present invention as compared to without using an additive.

Polymers 1-9 were generally synthesized by the following procedure(using Polymer 6 as an example) starting with appropriate monomers inthe required quantities. Isolation conditions vary depending upon thesolubility of the resulting polymers. Normally, multiple precipitationsinto hexane or methanol were used when possible. Otherwise, analternative isolation techniques such as that described was used.

3,5-Bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)phenyl methacrylate(3.0 grams, 6.07 mmol), and 8 mL of tetrahydrofuran (THF) were placed ina round bottom flask equipped with a condenser and a nitrogen inlet.2,2′-azobisisobutyronitrile (AIBN) (0.0399 grams, 0.243 mmol) was addedto this solution and stirred until dissolved. The solution was thendegassed using three vacuum/nitrogen purges. The contents were thenheated to reflux for 12 hours. Afterwards, hexanes were added to thesolution and the solvent was then removed in vacuo until a thick viscoussyrup was obtained. The resulting viscous syrup was added to hexanes andstirred vigorously for several hours. The hexane was decanted and freshhexane added. This process was repeated several times after which thepolymer flakes/powder stirred freely in the suspension and werenon-tacky. The polymer was collected by filtering through a fitted glassfilter, after which it was dried under vacuum at 80° C. overnight toafford 2.13 g (71% isolated yield) as a white powder.

Polymer 1: Synthesis ofpoly(3,5-bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)cyclohexylmethacrylate) (BisHFACHMA)

M_(n)=162,480. PDI=3.29. Tg: 179° C. n (193 nm)=1.501. α₁₀ (193nm)=0.099 μm⁻¹. Dissolution rate=1066 nm/s.

Polymer 2: Synthesis ofpoly(3,5-bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)cyclohexylmethacrylate-co-vinyl sulfonic acid) (BisHFACHMA/VSA)

M_(n)=5773. PDI=1.28. Tg: 139° C. n (193 nm)=1.512. α₁₀ (193 nm)=0.011μm⁻¹.

Polymer 3: Synthesis ofpoly(3,5-bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)cyclohexylmethacrylate-co-methyl methacrylate) (BisHFACHMA/MMA)

M_(n)=26157. PDI=2.16. n (193 nm)=1.511. α₁₀ (193 nm)=0.062 μm⁻¹.

Polymer 4: Synthesis ofpoly(3,5-bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)cyclohexylmethacrylate-co-1,1,1,3,3,3-hexafluoroisprop-2-yl methacrylate)(BisHFACHMA/HFIPMA)

M_(n)=5134. PDI=1.51. Tg: 100° C. n (193 nm)=1.506. α₁₀ (193 nm)=0.157μm⁻¹. Dissolution rate=540 nm/s.

Polymer 5: Synthesis ofpoly(3,5-bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)cyclohexylmethacrylate-co-1,1,1,2,2,3,3-heptafluorobut-4-ylmethacrylate)(BisHFACHMA/HFBuMA)

M_(n)=5587. PDI=1.60. Tg: 113° C. n (193 nm)=1.504. α₁₀ (193 nm)=0.112μm⁻¹. Dissolution rate=65 nm/s.

Polymer 6: Synthesis ofpoly(3,5-bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)phenylmethacrylate) (BISHFAPHMA)

M_(n)=8525. PDI=1.79. Tg: 132.7° C. n (193 nm)=1.747. α₁₀ (193 nm)=8.643μm⁻¹. Dissolution rate=3050 nm/s.

Polymer 7: Synthesis ofpoly(3,5-bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)phenylmethacrylate-co-1,1,1,3,3,3-hexafluoroisoprop-2-ylmethacrylate)(BisHFAPHMA/HFIPMA)

M_(n)=10552. PDI=1.74. Tg: 122.6° C. n (193 nm)=1.644. α₁₀ (193nm)=6.903 μm⁻¹.

Polymer 8: Synthesis ofpoly(3,5-bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)cyclohexylmethacrylate-co-2,3,4,5,6-pentafluorostyrene) (BisHFACHMA/PFS)

M_(n)=14058. PDI=1.70. Tg: 147.6° C. n (193 nm)=1.612. α₁₀ (193nm)=2.005 μm⁻¹.

Polymer 9: Synthesis ofpoly(3,5-bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)styrene(BisHFASTY)

Tg: none observable up to 200° C. n (193 nm)=1.569. α₁₀ (193 nm)=14.526μm⁻¹. Dissolution rate=8260 nm/s.

Polymers 10-13 were synthesized according to the general proceduresreported by Ito and Sundberg in US2006/0292484 A1, which is incorporatedherein by reference.

Polymer 10: Synthesis ofpoly(3,5-bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)trifluoromethacrylate-co-3,5-bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)cyclohexylvinyl ether) (BisHFACHTFMA/BisHFACHVE)

M_(n)=35,000. PDI=1.89. Tg: 164° C.

Polymer 11: Synthesis ofpoly(3,5-bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)cyclohexyltrifluoromethacrylate-co-1,1,1,2,2,3,3,4,4-nonafluorohex-6-ylmethacrylate) (BisHFACHMA/NFHVE)

Tg: 104.4° C. n (193 nm)=1.461. α₁₀ (193 nm)=0.006 μm⁻¹.

Polymer 12: Synthesis ofpoly(3,5-bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)cyclohexylmethacrylate-co-1,1,1,3,3,3-hexafluoroisoprop-2-yltrifluoromethacrylate-co-1,1,1,2,2,3,3,4,4-nonafluorohex-6-ylmethacrylate) (BisHFACHTFMA/HFIPTFMA/NFHVE)

M_(n)=66269. PDI=2.71. Tg: 80° C. n (193 nm)=1.454. α₁₀ (193 nm)=0.167μm⁻¹.

Polymer 13: Synthesis ofpoly(3,5-bis(1,1,1,3,3,3-hexafluoroisopropan-2-ol-2-yl)cyclohexylmethacrylate-co-t-butyltrifluoromethacrylate-co-1,1,1,2,2,3,3,4,4-nonafluorohex-6-ylmethacrylate) (BisHFACHTFMA/TBUTFMA/NFHVE)

M_(n)=29950. PDI=2.13. Tg: 82-84° C. n (193 nm)=1.457. α₁₀ (193nm)=0.061 μm⁻¹.

The contact angles of a variety of fluoroalcohol-functionalizedmethacrylate polymers are shown in FIG. 2. The structures are shownbelow:

The influence of structure on the water contact angles offluoroalcohol-based methacrylates has been reported (Sanders et al.,Proc. SPIE, 6159:615904 (2007)). However, it can be seen in FIG. 2, thepreferred fluoroalcohol structures for increased contact angles withhydrocarbons are significantly different than those preferred forwater-based applications. The 3,5-bis(hexafluoroisopropanol)cyclohexylmethacrylate structure is unique due to its high receding contact angleswith the hydrocarbon fluids and acceptable glass transition temperature.

The bis(hexafluoroisopropanol)cyclohexyl methacrylate structure was usedas the basis for a number of additive polymers incorporating variousother hydrophilic, hydrophobic, and latent acidic comonomers. Thecontact angles of these 3,5-bis(hexafluoroisopropanol)cyclohexylmethacrylate-based additive polymers were measured as described infrausing water, JSR HIL-001 (a commercial high index immersion fluid), andbicyclohexyl. The results are shown in FIG. 3.

Fluorinated comonomers such as HFIPMA and F7BuMA can be used to increasehydrophobicity, surface activity, and fluid contact angles (see polymers4 and 5); however, at high comonomer loadings, the additives becomeinsoluble in developer. Another method to boost hydrophobicity, surfaceactivity, and fluid contact angles is to decrease hydrocarbon groups andincrease fluorocarbon content by using a trifluoromethacrylate-vinylether backbone (Polymers 10-13). Finally, the incorporation of latentacidic groups affords the highest hydrophobicity, surface activity, andfluid contact angles. These latent acidic groups (like the t-butyl esterin Polymer 13) are deprotected in the exposed regions to form carboxylicacid groups which can react with developer to confer aqueous basesolubility. The photospeed of the additive with latent acidic groups maybe adjusted by using protecting groups with lower activation energies(such as 1-ethyl cyclopentyl or tetrahydropyranyl or t-butoxy carbonyl).It is preferable to have the photospeed of the additive be faster (or atleast equal) to that of the photoresist.

Comparison with a base-soluble conventional topcoat material (JSRTCX-014) and a base-soluble fluoroalcohol-based polymer (Asahi GlassFGC-400) reveals that the bis(hexafluoroisopropanol)-based polymersoffer superior contact angles with both JSR HIL-001 and bicyclohexyl. Infact, the performance reaches levels that heretofore have only beenachieved by highly fluorinated topcoat polymers like TOK TSP-3A that areinsoluble in conventional aqueous base developer and require exoticstripping solvents.

Several polymers from FIG. 3 were added to JSR 1682J (5 wt % relative tosolids content of the resist formulation) and the contact anglesreported in FIG. 4. Conventional 193 nm photoresists (typified but JSRAR1682J) show moderate water contact angles and extremely low contactangles with hydrocarbon fluids (<5 degrees). Without any surfacemodification, hydrocarbon immersion fluids will exhibit film pulling atextremely low scan rates (<50 mm/s) on these surfaces. While additivessuch as CHiPrHFAMA or ECPMA/3FMA (poly(1-ethyl cyclopentylmethacrylate-co-2,2,2-trifluoroethyl methacrylate) (70:30)), which weredesigned for use with water, show extremely high receding water contactangles, they offer only poor/moderate receding contact angles with JSRHIL-001 or bicyclohexyl. In marked contrast, thebis(hexafluoroisopropanol)-based additives (Polymers 7, 8, 11, and 13)exhibit slightly lower receding water contact angles, but much increasedreceding contact angles with hydrocarbon fluids.

Variable angle scanning ellipsometry (VASE) was used to model theprofile of surface enrichment layer in the blend of JSR AR1682J andPolymer 11 (5 weight % relative to resist solids content). Referring toFIG. 5, several potential fitting models were used to analyze theresults and the model with the lowest mean square error was a dual layerwith an intermixing layer. This indicates the photoresist film containsa surface fluoropolymer layer that is approximately 2 nm thick with an 8nm intermixing zone.

While clear surface enrichment of the bis(hexafluoroisopropanol)-basedadditives is observed by contact angle and ellipsometry, these types ofadditives do not effectively prevent photoacid generator (PAG) leachingin water immersion lithography as shown in FIG. 6. The high levels ofPAG leaching into water found for resists blends with3,5-bis(hexafluoroisopropanol)cyclohexyl-based acrylic polymer additivesis often evidenced by scumming and t-topping of the resist profiles whenthe compositions are imaged using water-based immersion lithography. Asa result, these additives are not useful for water immersionlithography; however, the much lower solubility and extraction rates ofcommon ionic PAGs in hydrocarbon-based high index immersion fluids willallow these additives to function adequately in high index immersionlithography. This is demonstrated by the difference in imagingperformance using water and high index immersion fluids shown in FIG. 7due to the negligible PAG extraction into hydrocarbon immersion fluidsobserved when polymer 11 is used as an additive (shown in FIG. 6).

The refractive indices of the polymers as determined by VASE are givenin FIG. 8. In applications where the thin enrichment layer of a lowrefractive index polymer may prohibit good lithography due to poorsurface reflectivity, the refractive index may be boosted byincorporating fluorinated aromatic monomers (e.g., pentafluorostyrene inPolymer 8 or 3,5-bis(hexafluoroisopropanol)phenyl methacrylate inPolymers 6 and 7). These fluorinated styrenic compounds feature highrefractive indices (n) at 193 nm while having unusually low absorbanceat 193 nm relative to their non-fluorinated counterparts likepolystyrene and poly(4-hydroxystyrene) as shown in FIG. 8. These resultsof adding the fluorinated aromatic monomers are refractive indices thatapproach or match that of current high index immersion fluids(n.about.1.64-1.65 at 193 nm).

To test the impact of these additives on the lithographic performance ofa photoresist, selected additives were mixed with JSR AR1682J-10 (atypical 193 nm photoresist). Five weight percent of additive was addedrelative to the solids content of the photoresist solution. Films werespun cast onto silicon wafers coated with 780 Å of ARC29a (BrewerScience) at 3000 rpm for 30 seconds and baked at 110° C. for 90 seconds.Referring to FIG. 9, contrast curves were measured using open-fieldexposures imaged on an ISI 193 nm mini-stepper (0.6 NA). The exposedresist was baked at 110° C. for 90 seconds and then the patterns werepuddle developed for 60 seconds using Optiyield CD (Air Products). Theresults are shown in FIG. 9. The results show that the presence of theadditive has only minor impact on the contrast and dose-to-clear. 193 nmimmersion interference lithography using JSR HIL-001 immersion fluid wasused to further demonstrate the imaging performance of these materialsas shown in FIG. 10. In this case, the composition with polymer 11 as anadditive shows nice square profiles which are superior to the roundedprofiles afforded by TCX-014 or the slightly t-topped profiles providedby the composition using the poly(l-ethyl cyclopentylmethacrylate-co-2,2,2-trifluoroethyl methacrylate (ECPMA/3FMA) (70:30)additive. The composition with polymer 13 as an additive does showextensive line bridging due to the high activation energy of the t-butylprotecting groups. Using a lower activation energy protecting group suchas 1-ethyl cyclopentyl is expected to resolve this issue as is apparentto those skilled in the art.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Recitation of ranges of values herein are merely intended toserve as a shorthand method of referring individually to each separatevalue falling within the range, unless otherwise indicated herein, andeach separate value is incorporated into the specification as if it wereindividually recited herein. The use of any and all examples, orexemplary language (e.g., “such as”) provided herein, is intended merelyto better illuminate the invention and does not pose a limitation on thescope of the invention unless otherwise claimed. No language in thespecification should be construed as indicating any non-claimed elementas essential to the practice of the invention.

The description of the embodiments of the present invention is givenabove for the understanding of the present invention. It will beunderstood that the invention is not limited to the particularembodiments described herein, but is capable of various modifications,rearrangements and substitutions as will now become apparent to thoseskilled in the art without departing from the scope of the invention.Therefore, it is intended that the following claims cover all suchmodifications and changes as fall within the true spirit and scope ofthe invention.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Recitation of ranges of values herein are merely intended toserve as a shorthand method of referring individually to each separatevalue falling within the range, unless otherwise indicated herein, andeach separate value is incorporated into the specification as if it wereindividually recited herein. The use of any and all examples, orexemplary language (e.g., “such as”) provided herein, is intended merelyto better illuminate the invention and does not pose a limitation on thescope of the invention unless otherwise claimed. No language in thespecification should be construed as indicating any non-claimed elementas essential to the practice of the invention.

The description of the embodiments of the present invention is givenabove for the understanding of the present invention. It will beunderstood that the invention is not limited to the particularembodiments described herein, but is capable of various modifications,rearrangements and substitutions as will now become apparent to thoseskilled in the art without departing from the scope of the invention.Therefore, it is intended that the following claims cover all suchmodifications and changes as fall within the true spirit and scope ofthe invention.

We claim:
 1. A composition comprising a photoresist polymer and afluoropolymer, the fluoropolymer comprising a first monomer selectedfrom acrylate and methacrylate having an aryl bis-hexafluoroisopropanolpendant group and a second monomer selected from fluorinated styrene andfluorinated vinyl ether.
 2. The composition of claim 1, wherein thephotoresist polymer suitably comprises repeat units having a carboxylicacid group protected with a photoacid cleavable group.
 3. Thecomposition of claim 1, wherein the photoresist polymer is selected fromthe group consisting of acrylates, methacrylates, cycloolefin polymers,cycloolefin maleic anhydride copolymers, cycloolefin vinyl ethercopolymers, siloxanes, silsesquioxanes, carbosilanes, polyhedraloligomeric silsesquioxanes, and carbohydrates.
 4. The composition ofclaim 1, wherein the fluoropolymer comprises a first monomer having thependant group C₆₋₁₀ aryl bis-hexafluoroisopropanol.
 5. The compositionof claim 1, wherein the first and second monomer comprises at leastabout 80 mole % of the fluoropolymer.
 6. The composition of claim 1,further comprising a photoacid generator (PAG).
 7. The composition ofclaim 6, wherein the PAG is selected from the group consisting ofsulfonates, onium salts, aromatic diazonium salts, sulfonium salts,diaryliodonium salts and sulfonic acid esters of N-hydroxyamides orN-hydroxyimides.
 8. The composition of claim 1, further comprising acasting solvent.
 9. The composition of claim 1, further comprising anadditive selected from the group consisting of dissolution inhibitors,dyes, sensitizers, stabilizers, dissolution modifiers, acid-diffusioncontrolling agents, bases, quenchers, surfactants, anti-foaming agents,crosslinking agents, photospeed control agents, adhesion promoters, andplasticizers.
 10. A composition comprising a photoresist polymer and afluoropolymer, the fluoropolymer comprising: (i) a first monomer havinga formula selected from:

wherein R₁, R₂, R₄, and R₅ are independently selected from hydrido andfluoro; R₃ and R₆ are independently selected from hydrido, fluoro,methyl and trifluoromethyl; X₁ is a linking group selected from oxy,thio, carbonyloxy, oxycarbonyl, carbonylthio, sulfonyl, carbonylamino,alkylene, cycloalkylene, fluorinated alkylene, fluorinatedcycloalkylene, alkyleneoxyalkylene, heteroalkylene, phenylene,fluorinated phenylene, naphthylene and fluorinated naphthylene; and Y₁and Y₂ are independently selected from C₁₋₁₀ alkylene, C₁₋₁₀cycloalkylene, phenylene and naphthylene each optionally substitutedwith fluorine wherein the first monomer comprises at least onemethacrylate having an aryl bis-hexafluoroisopropanol pendant group; and(ii) a second monomer having a formula selected from:

wherein R₇, R₈, R₁₀, and R₁₁ are independently selected from hydrido andfluoro; R₉ and R₁₂ are independently selected from hydrido, fluoro,methyl, and trifluoromethyl; X₃ is a linking group selected from oxy,thio, carbonylthio, sulfonyl, carbonylamino, cycloalkylene, fluorinatedalkylene, fluorinated cycloalkylene, alkyleneoxyalkylene,hetereoalkylene, phenylene, naphthylene, fluorinated phenylene, andfluorinated naphthylene; m and n are each independently selected from 0and 1; X₄ is a linking group selected from thio, carbonylthio, sulfonyl,carbonylamino, cycloalkylene, fluorinated alkylene, fluorinatedcycloalkylene, alkyleneoxyalkylene, hetereoalkylene, phenylene,naphthylene, fluorinated phenylene, and fluorinated naphthylene; m and nare each independently selected from 0 and 1; Y₃ is a substituentselected from alkoxy, cycloalkoxy, hydroxycarbonyl, hydroxysulfonyl,hydroxyphenyl, hydroxynaphthyl, fluorinated sulfonamidyl, hydroxyamidyl,carbamoyl, and alkylcarbamoyl; and Y₄ is selected from hydrido, fluoro,alkyl, fluoroalcohol, and fluorinated naphthyl.
 11. The composition ofclaim 10, wherein X₁ is selected from oxy, carbonyloxy, carbonylthio,fluorinated C₅₋₈ cycloalkylene, and fluorinated phenylene.
 12. Thecomposition of claim 10, wherein Y₁ and Y₂ are selected from C₅₋₈cycloalkyl and phenylene each optionally substituted with fluorine. 13.The composition of claim 10, wherein the first and second monomercomprises at least about 80 mole % of the fluoropolymer.
 14. Thecomposition of claim 10, wherein the photoresist polymer suitablycomprises repeat units having a carboxylic acid group protected with aphotoacid cleavable group.
 15. The composition of claim 10, wherein thephotoresist polymer is selected from the group consisting of acrylates,methacrylates, cycloolefin polymers, cycloolefin maleic anhydridecopolymers, cycloolefin vinyl ether copolymers, siloxanes,silsesquioxanes, carbosilanes, polyhedral oligomeric silsesquioxanes,and carbohydrates.
 16. The composition of claim 10, further comprising aphotoacid generator (PAG).
 17. The composition of claim 16, wherein thePAG is selected from the group consisting of sulfonates, onium salts,aromatic diazonium salts, sulfonium salts, diaryliodonium salts andsulfonic acid esters of N-hydroxyamides or N-hydroxyimides.
 18. Thecomposition of claim 10, further comprising a casting solvent.
 19. Thecomposition of claim 10, further comprising an additive selected fromthe group consisting of dissolution inhibitors, dyes, sensitizers,stabilizers, dissolution modifiers, acid-diffusion controlling agents,bases, quenchers, surfactants, anti-foaming agents, crosslinking agents,photospeed control agents, adhesion promoters, and plasticizers.